Process of coating steel sheets with aluminum



V adhere to" the I oial precautions are taken. If to remedy UNITEDsrarrs PATENT": orrice.

MENTS, TO WHEELING STEEL & IRON COMPANY, OF

A. CORPORATION OF WEST VIRGINIA.

WHEELING, WEST VIRGINIA,

PROCESS OF COATING STEEL SHEETS WITH AL'UMINUM,

No Drawing.

To all whom it may concern:

Be it known that I, SAMUEL PEAGOCK. a citizen of the United States.residing at Wheeling, in the county of Ohio and State of West Virginia,have invented certain new and useful Improvements in Processes ofCoating Steel Sheets with Aluminum; and I do hereby declare thefollowing to be a full, clear, and exact description of the invention,such as will enable others skilled 1n the art to which it appertains tomake and use the same.

This invention relates to a process of coating thin steel sheets withaluminum and has for its object to provide a procedure which will bemore efiicient in action and less costly to carry out than those whichhave been heretofore proposed.

With these'and other objects in view the invention consists in the novelsteps and combinations of steps constituting the process, all as will bemore fully hereinafter disclosed and particularly pointed out in theclaims.

In order that the precise invention may be the more clearly understood,it is said: It is well known that thin sheets of steel after beingdescaled or cleaned according to well known procedures are now commonlyimmersed in a bath of molten tin, inorder to convert them into the tinplate of commerce. The tin of the coating, however, is a largeitem ofcost when it is considered that these sheets are treated by the million,and in addition, said coating entails other well known objections notnecessary to mention. A

It is therefore the object of this invention more specifically stated,to coat said sheets with aluminum and thus obviate many of theobjections that are now met with in the tin coating processes.

But in coating said sheets by dipping them into a molten bath ofaluminum, the

relatively high temperature of about 700? C. of the latter causes manypractical d fliculties in obtaining a good coating, which greatlyincrease the cost of the procedure. 1

That is to say, the differences in temperature between the steel andaluminum are considerable and the coating is not apt to steelthroughout,-:unless spe- Specification of Letters Patent.

Application filed November 9, 1920. Serial No. 422,812.,

Patented May 17, 1921.

this objection, we pass the steelsheets through the molten aluminumslowly enoughfor the steel sheets to reach the temperature of the bath,and to form an alloy film to hold the coating, the process will be foundto be too slow to be commercial.

On the other hand, a rapid passage of the steel sheets through themolten bath will result in a coating consisting of a solidified, orfrozen la er, almost devoid, of a film of alloy to hold it to the sheet,and possessing a considerable structure.

In carrying out this invention, I avoid the foregoing objections byemploying 011 top of the molten aluminum a molten layer of an anhydrousdouble alkali aluminum porosity .due to a crystalline,

chlorid such as AlNaCh, which has a melting point of about 200 C. Ifurther employ the usual apparatus for coating with tin, consisting of aseries of submerged guide and traction rolls to carry the steel sheetsinto and out of the aluminum bath. The double aluminum sodium chloridlayer or bath is preferably maintained at about 300 C. on top of thealuminum by means of cooling coils. The steel sheets being freed fromtheir oxids, or cleaned, are now heated up in a non-oxidizingatmosphere, or out of contact with the air, to a temperature of say 250C. or 300 C. or higher, whereupon they are carried through the saiddouble chlorid layer into the aluminum bath. Said double aluminum alkalichlorid is found to readily deposit a firmly adhering film on the. steelsheets as they pass into the aluminum, and the molten aluminum readilycoats said filmwith a firmly adhering film of aluminum, as said sheetspass therethrough, with the result that the finonv the molten aluminum,however, -all contact with the air is avoided and thewcoating isthereforegreatly improved. Again, as is well known in coating proceduresof this kind it-is very desirable to pass the coated,

sheets throu h palm oil as they leave the apparatus. t is found thatinstead of having a single double chlorid bath, two may be provided. Theone is positioned on that side of the machine at which the steel platesenter the bath of aluminum, and the other Y is positioned on the exitside of the maplates therewith, as they leave the apparatus. 1

It is obvious that those skilled in the art may vary the details of theprocedure without departing from .the spirit of the invention, andtherefore it is not desired to be limited to the above disclosure exceptas may be required by the claims.

What is .claimed is:

1. The process ofcoating steel sheets with aluminum which consists infirst passing said sheets through a molten bath of a double aluminumalkali metal chlorid, and then through a molten bath of aluminum}substantially as described.

2. Tlidprocessof coating steel sheets with aluminum which consists infirst depriving said sheets of any oxid coating they may have, thenpassing said sheets through a substantially as described.

i said baths in the order named, substantially as described.

4. The process of coating steel sheets with aluminum which consists infloating a molf ten bath of a double aluminum alkali metal chlorid upona molten bath of aluminum; maintaining the temperature of said firstnamed bath below that of saidsecond named bath; heating said sheets tothe approximate temperature of said first named bath; and passing saidsheets through said baths in the order named, substantially a described.

5. The process of coating steel s eets with aluminum which consists infloating a molten bath of a double aluminum alkali metal chlorid upon amolten bath of aluminum; maintaining'the temperature of said first namedbath below that of said second named bath; passing said sheets throughsaid baths in the order named; and thin passing the coated sheetsthrough a bat In testimony whereof I afiix my signature.

SAMUEL PEACOCK.

of palm oil,

